Recently, the number of subscribers to broadband Internet connection services such as ADSL (Asymmetric Digital Subscriber Line) and FTTH (Fiber To The Home) in Japan reached approximately 1,5000,000. In recent years, wired or wireless home networks have been installed at a rapid pace so that members of a family can be in a broadband environment in any place in the house.
Under such circumstances, it has become possible that a family member can use an AV (Audio Visual) device in the home to enjoy a remote viewing of a digital content that is stored and accumulated in another AV device, or can change the location where digital contents are stored and accumulated.
It should be noted here that the digital contents handled by such AV devices can easily be copied and are hardly degraded in the quality by the copying. If the contents copied in an unauthorized manner are distributed unlimitedly, the economical advantage of the content creators is infringed. And if such advantage is not guaranteed, there is a fear that good contents may not be circulated smoothly. When this happens, general users may not be able to acquire good contents. To solve the problem of the unauthorized copying of contents, contents protection technologies, such as EEE1394 bus and IP network DTCP (Digital Transmission Content Protection), have been introduced into the AV devices that handle digital contents on the home network. However, conventional technologies such as DTCP have a problem that the copy of contents is restricted even within a range of private uses in which users should be allowed to copy contents freely.
Document 1 acknowledged below discloses a management method in which a content is permitted to be copied up to a predetermined number of times, by managing the number of copies or moves of a content as additional information.
Also, Document 2 acknowledged below has introduced a temporal concept into the limited use of a copied content that was copied from a content stored in a device, and according to the method disclosed in the document, the device allows the copied content to be used only in a usable period, and inhibits copying from the content during the copied content usable period. In this method in which the device inhibits copying from the content during the copied content usable period, the number of copies is limited to one.    Document 1: Japanese Patent Application Publication No. 2003-22338.    Document 2: Japanese Patent Application Publication No. 2000-305854.